1972 Marker and running lights

[david7w5@gmail.com]

I have a 1972 C30, when I turn on the first pull of the marker lights, the front side and bumper lights does not light up. It has a flat bed so no rear marker light. My headlights work, rear taillights, brake lights, and hazard lights work. When I turn on the blinker the front marker light flashes.

I owned a 69 in the past and the marker lights didn't flash.

What would cause this problem?